Hard mask films are used for etching deep, high aspect ratio (HAR) features that conventional photoresists cannot withstand. Amorphous Carbon is currently used as a hard mask layer to provide high etch selectivity to organic materials such as photoresist, dielectric materials such as SiO2, SiN, and low-k dielectric materials. Due to the increasing thickness of under layer films, the thickness of hard mask continues to increase.
Moreover, amorphous carbon films are usually non-transparent materials having high extinction coefficients. This poses a significant problem for the purpose of overlay alignment during lithography processes.
Therefore, there is a need in the art for new hard mask materials with better conformality and etch selectivity over conventional materials.